Furthermore, opening the app itself will show a blank screen until you start granting permissions. For example, say you launch an app that requires SU permission. You click always allow. Now when you go back into the SU app you should see something listed.

I ran into this too. I forget the exact. Order of these steps but if my memory. Serves me I disabled debugging and shut the phone off. Then I turned the phone back on and enabled debugging and I had SU and could use root explorer from then on.
Good luck.